Volume 2: Uninterrupted Flow

Chapter 10: Freeway Facilities

Chapter 10, Freeway Facilities, provides a methodology for analyzing extended lengths of freeway composed of continuously connected basic freeway, weaving, merge, and diverge segments. Such extended lengths are referred to as a freeway facility. In this terminology, the term facility does not refer to an entire freeway from beginning to end; instead, it refers to a specific set of connected segments that have been identified for analysis. In addition, the term does not refer to a freeway system consisting of several interconnected freeways.

Chapter 11: Basic Freeway Segments

Chapter 11, Basic Freeway Segments, provides a methodology for analyzing the capacity and level of service (LOS) of existing or planned basic freeway segments. The methodology can also be used for design applications, where the number of lanes needed to provide a target LOS for an existing or projected demand flow rate can be found.

Chapter 12: Freeway Weaving Segments

Chapter 12, Freeway Weaving Segments, provides a methodology for analyzing the operation of weaving segments based on these characteristics as well as a segment’s free-flow speed (FFS) and the demand flow rates for each movement within a weaving segment (e.g., ramp to freeway or ramp to ramp). This chapter describes how the methodology can be applied to planning, operations, and design applications and provides examples of these applications.

Chapter 13: Freeway Merge and Diverge Segments

Chapter 13, Freeway Merge and Diverge Segments, focus on ramp–freeway junctions, but guidance is also provided to allow approximate use of such procedures on multilane highways and on C-D roadways.

Chapter 14: Multilane Highways

Chapter 14, Multilane Highways, addresses capacity and level-of-service (LOS) analysis for uninterrupted-flow segments of surface multilane highways. In general, uninterrupted flow may exist on a multilane highway if there are 2 mi or more between traffic signals. Where signals are more closely spaced, the facility should be analyzed as an urban street.

Chapter 15: Two-Lane Highways

Chapter 15, Two-Lane Highways, presents methodologies for the analysis, design, and planning of two-lane highway facilities operating under uninterrupted flow, for both automobiles and bicycles. Uninterrupted flow exists when there are no traffic control devices that interrupt traffic and where no platoons are formed by upstream signals. In general, any segment that is 2.0 to 3.0 mi from the nearest signalized intersection would fit into this category. Where signalized intersections are less than 2.0 mi apart, the facility should be classified as an urban street and analyzed with the methodologies of Chapter 16, Urban Street Facilities, and Chapter 17, Urban Street Segments, which are located in Volume 3. It is assumed that no passing in the opposing lane occurs on urban streets.

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